I. Field of the Invention
This invention relates generally to spine surgery and, in particular, to methods and apparatus for treating spinal stenosis.
II. Discussion of the Prior Art
Spinal stenosis is a narrowing of spaces in the spine which results in pressure on the spinal cord and/or nerve roots. This disorder usually involves the narrowing of one or more of the following: (1) the canal in the center of the vertebral column through which the spinal cord and nerve roots run, (2) the canals at the base or roots of nerves branching out from the spinal cord, or (3) the openings between vertebrae through which nerves leave the spine and go to other parts of the body.
Pressure on the lower part of the spinal cord, or on nerve roots branching out from that area, may give rise to pain or numbness in the legs. Pressure on the upper part of the spinal cord (neck area) may produce similar symptoms in the shoulders, or even the legs. The condition generally occurs in patients who are in their last decade or decades of life.
Laminectomy, which involves removing bone, the lamina, from the vertebrae, is the most common surgical treatment for spinal stenosis. Laminectomy enlarges the spinal canal, thus relieving the pressure on compressed nerves. Surgical burs, drills, punches, and chisels are used during the procedure.
Surgeons risk injuring the nerves or the spinal cord as they enlarge the spinal canal. In addition, elderly patients frequently have co-morbidities that increase the risk of laminectomy. Complications of laminectomy include increased back pain, infection, nerve injury, blood clots, paralysis, prolonged recovery, and death.
Lumbar fusion is frequently preformed in conjunction with laminectomy. Current fusion techniques require abrasion of large surfaces of bone. Bone bleeds during and after abrasion. Current fusion techniques increase the risk of spinal stenosis procedures. Fusion also prolongs patient recovery following spinal stenosis surgery. Furthermore, various fusion techniques require the severing and/or removal of certain soft tissue surrounding the spine, including but not limited to the supraspinous ligament, the intraspinous ligament, the ligamentum flavum, the posterior longitudinal ligament, and/or the anterior longitudinal ligament.
Increasingly, surgeons are looking for improved methods of effecting less invasive treatments for spinal stenosis. The device must be able to be safely and consistently implanted without excess damage to the patient. The present invention is directed at overcoming, or at least improving upon, the disadvantages of the prior art.